Field of the Invention
This invention relates to a wireless communication system in which one radio access technology operates in conjunction with a second radio access technology. The invention has particular, but not exclusive, relevance to the co-existence of a GSM public land mobile network (PLMN) and an LTE or LTE-advanced PLMN.
Description of the Related Technology
Although LTE offers a number of advantages over older mobile communication standards, there is a need to maintain GSM coverage for voice calls and also for legacy telematics systems which utilize the GSM communication network.
An LTE signal can have a system bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz, and is centered at a frequency that is a multiple of 100 kHz. In the time domain an LTE signal is divided into contiguous radio frames of 10 ms duration. As shown in FIG. 4, each radio frame is made up of 10 sub-frames, each subframe of 2 resource blocks (RBs), which in turn are made up of a number of symbols. So, in the time domain a resource block is 0.5 ms in duration. In the frequency domain a resource block is 180 kHz wide, corresponding to 12 subcarriers, each separated by 15 kHz. There are 6, 15, 25, 50, 75, and 100 resource blocks in the 1.4, 3, 5, 10, 15 or 20 MHz bandwidth systems respectively. Control data is scheduled across the system bandwidth of the LTE signal.
A GSM signal has a nominal bandwidth of 200 kHz centered at a frequency that is a multiple of 200 kHz.